• Proceedings of the Korean Reliability Society Conference
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• 2001.06a
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• pp.301-310
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• 2001

Lim et al.(1998) proposed the Bayesian Imperfect Repair Model, in which a failed system is perfectly repaired with probability P and is minimally repaired with probability 1 - P, where P is not fixed but a random variable with a prior distribution II(p). In this note, the steady state availability of the model is derived and the measure is obtained for several particular prior distribution functions.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.21 no.48
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• pp.113-122
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• 1998

In this paper we consider the CSP requirements determination problem of new equipment(machine) system. For the newly procured equipment systems, mathematical analyses are made for the system which is constructed with the consumable parts to derive the associated CSP requirement determination model in mathematical expression. Based on these analyses, a mathematical model is derived for making an optimal CSP requirement determination subject to tile constraint of satisfying any given operational availability limitation. We assume that the failure of a part follows a Poisson process. Firstly, the operational availability concept in CSP is defined and the relation between the general system availability and the operational availability is established. Secondly, the problem is formulated as the cost minimization problem that should satisfy the operational availability limitation, and then, using the generalized Lagrange multipliers method, the optimal solution procedure is derived.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.59
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• pp.53-67
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• 2000

In this paper we consider the CSP requirements determination problem of new equipment(machine) system. For the newly procured equipment systems, mathematical analyses are made for the system which is constructed with the consumable parts and the repairable parts to derive the associated CSP requirement determination model in mathematical expression. Based on these analyses, a mathematical model Is derived for making an optimal CSP requirement determination subject to the constraint of satisfying any given operational availability limitation. We assume that the failure of a part follows a Poisson process and the repair time has an exponential distribution. Firstly, the operational availability concept in CSP is defined and the relation between the general system availability and the operational availability is established. Secondly, the problem is formulated as the cost minimization problem that should satisfy the operational availability limitation, and then, using the generalized Lagrange multipliers method, the optimal solution procedure Is derived.

• Korean Management Science Review
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• v.24 no.2
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• pp.81-93
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• 2007

Achieving a target operational availability is more economical and efficient than having many quantities of the weapon system, since the cost of weapon system becomes expensive. The intent of this study is twofold; first, we develop the simulation model to determine the optimal inventory level of the maintenance float while achieving a target operational availability of the Korean-made helicopter. The quantity decision model considers following factors such as a reliability. a turn around time(TAT). a protection level for inventory, and so on. Second, we analyze whether the existence of a lateral transshipment among bases and the reduction of TAT relate to an inventory level and the operational availability. The research result shows that both TAT and lateral transshipment have an effect on reducing the inventory level of the maintenance float and improving an operational availability.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.5_6
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• pp.290-298
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• 2003

Internet-based computer systems have to provide both high-availability and high-performance. Cluster technology has been used to obtain availability and performance simultaneously Generally, high-availability cluster systems tolerate a failure of a cluster node and cost-effectively solve it. In this paper, we study availability and downtime cost of (n,k) cluster systems. By considering performance, we model state transition of (n,k) cluster systems and apply software rejuvenation technique to improve availability of the system. We find that software rejuvenation can be used to improve availability of (n,k) cluster systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2634-2639
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• 2014

The idea of redundancy is used in order to improve the availability of networks and systems and there are various methods for implementing redundancy. To perform the availability analysis various stochastic models have been used. In this paper, 2N redundancy with one active service unit and one standby service unit is considered. To evaluate the expected availability, we model 2N redundancy using Stochastic Reward Nets. This model can be solved using the SPNP package.

• Journal of the Korea Safety Management & Science
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• v.10 no.3
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• pp.89-98
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• 2008

A preventive maintenance model, caller FNBM($\alpha$, $\delta$, $\gamma$)model, is proposed to decide an optimal repair number under achieved availability requirements(r) along with taking two types of failures (repairable or irrepairable) into account. In this model, the current system is replaced by a new one in case when it doesn't meet the achieved availability requirement, even though it is repairable failure; Otherwise it is replaced in time of the first irrepairable failure. Assumed that the j-th failure is repairable with probability ${\alpha}_j$ minimal repairs are allowed for repairable failure between replacements. Expected cost rate for preventive maintenance model is developed using NHPP(Non-Homogeneous Poisson Process) in order to determine the optimal number $n^*$, also numerical examples are shown in order to explain the proposed model. Since the proposed FNBM($\alpha$, $\delta$, $\gamma$)model includes Park FNBM model(1979) and Nakagawa FNBM(p)model(1983) this proposed model is thought to be better than previous model, especially for weapon system which requires availability as primary parameter.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.1
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• pp.41-49
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• 2010

In this paper, we propose a hierarchical RAM simulation model framework which are used to analyze the RAM specifications on the concept refinement phase. The hierarchical RAM simulation model framework consists of RAM simulation models, class library and each model's input and output data lists. The hierarchical RAM simulation models are co-operated with 3 kinds of model - type I, II, III. Type I, II models are used to analyze the target operational availability and Type III is used to establish the initial RAM specifications. Each model's input and output data lists are defined by considering each model's purpose of RAM analysis. The class library is arranged with each model's classes for implementing the hierarchical simulation models. The proposed framework may be applied for executing the RAM activities effectively.

• Journal of Korean Society for Quality Management
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• v.38 no.3
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• pp.333-339
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• 2010

It is difficult to determine an optimal inventory level of aircraft engine and modules to achieve the target operational availability since F100-PW-200 & 229 engines of the F-16 & KF-16 aircraft are consisted of 5 modules with different failure rates and costs. This study presents a decision model, combining an integer programming problem and a regression metamodel. Data for the metamodel was attained from results of a simulation model, that represents operational and repair process of F-16 and KF-16. The objective function of an integer programming problem is maximizing the operational availability, representing pessimistic circumstances. Finally, an integer programming problem with a metamodel can make an optimal decision of the inventory level.

• The Transactions of the Korea Information Processing Society
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• v.7 no.3
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• pp.745-755
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• 2000

In designing distributed databases, DAP(Data Allocation Problem) is one of the key design issues. Because, however, most of previous researches on DAP have considered only cost aspect, they cannot increase the performance and availability and they are not proper to the system requiring high-availability or real-time processing. Therefore, we need a more formal data allocation model considering multiple aspects. In this paper, we propose the MAPN (Multiple Aspects Petri Net) modeling method for the distributed transaction modeling. The MAPN model, an extended classical petri net, is proposed for the formal modeling considering multiple aspects (cost, performance and availability) concurrently. We demonstrate that we can compose the valid DAP evaluation model considering not only cost but also performance and availability concurrently by using the MAPN structure and MAPN graph.